It's a big country, as they say, and no one knows that better than Philip Caputo. In "The Longest Road: Overland in Search of America, from Key West to the Arctic Ocean," the novelist, nonfiction writer and former Pulitzer Prize-winning reporter for the Chicago Tribune takes a four-month road trip from the southernmost point of the United States to its northernmost place reachable by car. Along the way, Caputo interviews Americans of a dizzying variety of backgrounds about what they think holds his huge — and hugely diverse — country together.

A native of Westchester and a graduate of Loyola University Chicago, Caputo will be appearing July 24 as part of the Tribune's literary series. Printers Row Journal caught up with the 72-year-old author — best known for his classic 1977 Vietnam memoir "A Rumor of War" — for a phone chat from his home in Norwalk, Conn. Here's an edited transcript of our chat.

Q: The seed of the book, I gather, was a trip to Alaska a while back.

A: Yes, I was there back in 1996, on a remote island off the Alaskan coast, and I happened to go by a school where most of the students were Eskimo children. They were pledging allegiance to the flag, and it struck me that they were doing so under the same government as the children of Cuban immigrants down in Key West, where I had been earlier in the year. It just astonished me that in a country so vast — the distance from that island in Alaska to the island of Key West is equivalent to the distance from New York to Moscow — those children were under the same government, spoke the same language and were united in the same kind of society.

Obviously there are cultural differences between the two, but the American society is the same. And I just thought to myself, what holds a place so vast and diverse together? I've been in so many countries, in my time as a foreign correspondent and just as a traveler, that had many different ethnic groups and races and religions, but they were at each other's throats, as we now see in Syria. And I thought, "My God, I could drive, if I wanted to, from Key West, the southernmost point in the continental U.S., all the way up to the Arctic Ocean at Dead Horse, Alaska. The thought went into the back of my mind, and didn't really awaken until 14 years later.

Q: What happened then?

A: It was shortly after my father had died at 94, and my own advancing age — I was approaching my 69th birthday — and mortality came into the front of my mind. And I thought back to that thought I'd had in Alaska, and I thought, "Why don't you do it? Why don't you make that drive, and find out what people think about that question?"

I was also motivated by the divisiveness that had come into American politics and society in fairly recent years, even to the point where some people in Texas and elsewhere were uttering the word "secession." I don't know how serious they were about it, but the mere fact that they were even entertaining the thought struck me as a sign of a society that was maybe starting to come unglued.

Q: And you thought, perhaps, "If I'm going to do this trip, I have to do it now"?

A: That's right. You know, I've lived my life on the axiom that the things you do don't cause half the regret as the things you fail to do.

Q: You decided to use an Airstream trailer on the trip, which seems to have had a special meaning for you.

A: The Airstream, to me, is the quintessential American road vehicle — especially an antique one like the one we rented, which was built in 1962. I looked at it as the modern highway equivalent of the prairie schooner or the Calistoga wagon. To me, it symbolized moving on, getting out into the territory.

Q: You also had to decide whether to bring your wife along.

A: My first thought was to go with just our two dogs. But it became obvious to me that on a trip of this magnitude — it was over 16,000 miles round-trip — I wasn't going to be able to handle a journey of that length, and take care of the dogs, and take care of the trailer, and to find people to interview and take notes, all by myself. So that was the practical reason for asking my wife to go along. Obviously there was an emotional reason as well, because I was going to be gone from her for about four months, and neither of us wanted that. So she took a leave of absence from her employer, and off we went.

Q: Did you have models in mind for the book, John Steinbeck's "Travels with Charley," for example, or William Least Heat-Moon's "Blue Highways"?

A: I had read those two books, as well as Jack Kerouac's "On the Road" and some others. But I had read them sometime earlier — I think I read "Travels with Charley" 30 years ago — so I can't call them models, exactly, but they were certainly inspirations. I did reread parts of them to remind myself of the level of prose that I wanted to reach with this book. I didn't want this to be just a "what I did on my summer vacation" essay.

Q: In the case of the Steinbeck book, as I'm sure you're aware, questions have arisen about the veracity of some of its episodes.

A: Yes, some have suggested that he wasn't really where he said he was, and perhaps didn't really talk to people that he claimed to have spoken to. I guess the evidence for some of that fictionalizing has been fairly strong, but nevertheless, there's a quality of Steinbeck's prose, and his insights into America and, really, into himself, that I held as a standard to follow. I did not, obviously, hold the fictionalizing as a standard to follow, and that's one of the reasons I brought along a digital recorder and downloaded all those interviews onto my laptop. It was to establish that I had really been to all these places and really spoken to these people. I'm too much of an old-style reporter to try to make that kind of stuff up.